Mixing apparatus



May 27, 1969 c. F. FISCHER 3,446,485

MIXING APPARATUS Filed Sept. 22, 1966 INVENTOR. CHARLES F. FISCHER Filed Sept. 22, 1966 y 1969 c. F. FISCHER 3,446,485

MIXING APPARATUS Sheet 3 of 4 I ENTOR. CHARLE FISCHER May 27, 1969 Filed Sept. 22. 1966 C. F. FISCHER MIXING APPARATUS INVENTOR. CHARLES E FISCHER y 27, 1969 c. F. FISCHER 3,446,485

MIXING APPARATUS Sheet of 4 Filed Sept. 22. 1966 INVENTOR. CHARLES F. FISCHER United States Patent 3,446,485 MIXING APPARATUS Charles Frederick Fischer, Jersey City, NJ., assignor to Colgate-Palmolive Company, New York, N.Y., a corporation of Delaware Continuation-impart of application Ser. No. 509,803,

Nov. 26, 1965. This application Sept. 22, 1966, Ser. No. 581,330

Int. Cl. B01f 15/02, 7/04 US. Cl. 259-6 19 Claims This application is a continuation-in-part of my application Ser. No. 509,803, filed Nov. 26, 1965. That application described twin-shaft paddle type mixing apparatus modified so that the material being processed therein was extruded, through a discharge passageway, in a direction transverse to the shafts.

In accordance with one aspect of this invention, the apparatus is further modified to provide more even extrusion and more intensive mixing.

Another aspect of this invention relates to the provision of paddles of improved construction.

Other aspects of this invention will be apparent from the following detailed description and claims.

FIG. 1 is a side view of the mixing apparatus;

FIG. 2 is a plan view partly in cross-section;

FIG. 3 is an end view of the mixing apparatus illustrating also two types of extrusion nozzles;

FIGS. 4-7 are cross-sectional views in elevation, taken perpendicular to the driven shifts of the mixing apparatus, and showing successive positions of its paddles;

FIG. 8 is a side view of a forwardly pitched paddle;

FIG. 9 is a fragmentary top view of the paddle of FIG. 8;

FIG. 10 is a view, partly in cross-section, taken perpendicular to the driven shafts looking toward the feed end, and illustrating the action of the forwardly pitched paddles;

FIG. 11 is a view, partly in cross-section, taken perpendicular to the driven shafts and illustrating the arrangements of a series of forwardly pitched paddles;

FIG. 12 is a side view of a non-pitched paddle;

FIG. 13 is a fragmentary top view of the paddle of FIG. 12;

'FIG. 14 is a side view of a rearwardly pitched paddle;

FIG. 15 is a fragmentary top view of the paddle of FIG. 14;

FIG. 16 is a view, partly in cross-section, of a modified type of paddle;

FIG. 17 is a view, partly in cross-section, taken perpendicular to the driven shafts, looking from the end wall 21, and illustrating the arrangement of a series of rearwardly pitched paddles;

FIG. 18 is a side view, partly in cross-section, of the feed end of a modified form of mixing apparatus;

FIGS. 19, 20 and 21 constitute an exploded perspective view of the discharge end of the apparatus, showing in FIGS. 20 and 21 the two different forms of extrusion nozzles also illustrated in FIG. 3;

FIG. 22 is a side view, broken away and partly in crosssection, showing a modified form of feed screw at the feed end of the apparatus;

FIG. 23 is a schematic side view showing an alternate arrangement of feeding devices;

FIG. 24 is a view of a modified extrusion nozzle arrangement.

Referring now to FIG. 1 of the drawing, reference numeral 11 designates a jacketed housing within which there are mounted a pair of parallel rotatable shafts 12 (FIG. 2) each extending horizontally the full length of the housing and each having mounted thereon, for rotation therewith, 'feed screw elements 13 and agitator ele- 3,446,485 Patented May 27, 1969 ments or paddles which are designated generically by the numeral 14, the paddles being of three types (F14, N14 and R14, FIGS. 8-15) as will be described more fully below. (In FIG. 2, only the paddles at the end portions of the shafts are illustrated; for simplicity, the intermediate paddles are not shown.) The longitudinal cavity within the housing is made up of two intersecting circular cylindrical zones (as can be seen from the end view in FIG. 4) each such cylindrical zone being coaxial with the rotatable shaft 12 situated in said zone; there being a small radial clearance between the inner walls of the cavity and the outer peripheries of the paddles and feed screw elements. There is an opening or hopper 16 (FIG. 1) at one end of the housing, above the feed screw elements, for introducing, into the cavity of the housing, the solid materials to be processed. In one embodiment of the invention, these solid materials are finely divided builder salts together with finely divided synthetic anionic detergent; the water to be blended with the solid ingredients to form a pasty mass is introduced under pressure through an opening 17.

The mixture is discharged from the housing 11 through one or more discharge openings situated adjacent its end wall 21. In one preferred form of the invention, the housing has two diametrically opposed openings 22, 23 of rectangular cross-section (see FIG. 19) to which are fitted a pair of elongated extrusion tubes as shown in FIGS. 20 and 21, through which tubes the mixture is extruded as a continuous bar.

In the form illustrated in FIG. 20, each extrusion tube 24 is tapered (e.g. frustoconical) and is fitted at its end with a die plate 26 having a rectangular opening 27. The conical tube 24 may be welded to a rectangular plate 28 adapted to be secured (as by suitable screws passing through holes 29) against a corresponding fiange 31 of the housing at the opening 22, 23. The die plate 26 is removably and interchangeably supported by a cap 32 screwed onto the end of the tube 24.

In FIG. 21 each of the two extrusion tubes 33, 33A is of substantially uniform cross-section along its length (the cross-section being preferably rectangular) is mounted,

as by welding, on a rectangular plate 34 adapted to be secured (like plate 28) against a flange 31 so that the openings 22, 23 are blocked by the plates 34 over most of their height.

The end wall 21 has circular holes 37 (FIG. 3) for snugly, but rotatably, receiving the shafts 12. Antifriction bearings for the shafts may be placed in these holes or in a supporting plate 38 (FIG. 1).

To provide access to the interior of the housing, the latter is made in two sections, namely, a stationary lower section 39 (FIG. 1) and a removable upper section 40 which is firmly but detachably secured to the lower section in any suitable manner, as by means of bolts 41 passing through matching flanges 42 of these two halves of the housing. The upper section 40 has a downwardly depending ridge 43 (FIG. 4) conforming to the portion above the intersection of the circular cylindrical zones, and the lower half has a similar upwardly projecting ridge 44.

The two shafts 12 are adapted to be driven in the same direction by a drive motor and gear arrangement 46 (FIG. 1) situated at one end of the housing. The feed screw elements 13 (FIG. 2) on the shafts are of conventional helical type, suitably intermeshing in well known fashion as the shafts rotate to advance the material, supplied through the hopper 16, in an axial direction towards the paddles.

The paddles 14 are arranged in matching pairs, the design being such that a tip 47 (FIG. 4) of one paddle of each pair is always moving in wiping relationship to an edge 48 of the other paddle of the pair during the continuous co-rotation of the shafts. In one particularly advantageous construction, the paddles of any pair are identical with each other and mounted with their long axes LA (FIG. 5) at right angles, the edges 48 of each paddle being defined by equiradical symmetrical arcs whose centers and O are symmetrically situated on the prolongations of the short axis SA of the paddle. These arcs are of greater radius than the radii of the cylindrical zones of the cavity in the housing. As will be seen from the sequence shown in FIGS. 4 to 7, during the co-rotation of the shafts about the rotational axes RA, one tip 47 of the left hand paddle follows along the edge or flank 48 of the right hand paddle, and then a tip of the right hand paddle moves in identical fashion along the edge of the left hand paddle. Thus, FIG. 5 is a view after a 45 rotation from the position shown in FIG. 4 and FIG. 6 shows the relationship after an additional 67 /2 of rotation, After a total rotation of 90 from the position shown in FIG. 5, the tip of the right hand paddle is adjacent to the other tip of the left paddle, as shown in FIG. 7. Thereafter, that tip of the left hand paddle moves in an identical fashion along an edge or flank of the right hand paddle. Thus, in a full 360 rotation, each edge of each paddle will be wiped once by a tip of its matching paddle. During this full 360 rotation, the internal walls of the housing will be wiped twice by the tips of the paddles.

Certain paddles 14 (hereinafter called forwardly pitched paddles, and hereafter designated F14) are designed to advance the material longitudinally of the shafts away from the feed end. To this end, the profile of the rear face 51 (FIG. 8) of the forwardly pitched paddle F14 is offset by a slight angle a (about the axis of rotation) from the profile of its front face 52 in the same direction as the direction of rotation of the paddles illustrated by the arrows in FIG. 8. For example, for a paddle having its long axis 4%. inches long and its short axis 2 inches long, and having a thickness of 1 inch, the two faces may be offset by an angle of 12 /2 The other paddle of the same pair has the profiles of its faces similarly offset by the identical angle, the design being such that the edge of each paddle will be wiped by the tip of its paired paddle, as previously described. Thus, in any cross-section through the pair of paddles, at right angles to the axis of rotation, the relationship of the crosssectional profiles will be the same as that shown in FIGS. 4 to 7.

The front and rear faces of all the paddles 14 are preferably flat and are situated in planes perpendicular to the shafts 12. In a preferred design, there is a smooth transition from the profile of the rear face 51 of each forwardly pitched paddle F14 to the profile of its front face 52 so that the flanks F48 of these paddles may each be considered to be generated by a continuous series of identical profiles, each infinitesimally angularly displaced from the adjacent profile, the angle of displacement (about the axis of rotation) increasing continuously from the rear to the front of the paddle until, at the front face, the angle has risen to the value of 0:. Thus, the leading portions of each of these flanks F48 (that is, the portions of the flanks visible at the upper left and lower right in FIG. 8, which leading portions are hereafter designated as F48L) are tilted or pitched with respect to the axis of the shaft on which the paddles are mounted, so that each of these leading portions F48L has the effect, like that of a fan blade, of urging the mixture through the housing in a direction away from the feed end. The pitch of the flanks of the paddles F14 is greatest at their tips F47. As these pitched tips wipe along the inner walls of the housing 11 and along the corresponding flanks of the mated paddle F14 (as shown in FIG. they and their adjacent pitched leading flank portions F48L will transfer the mixture, in a forward direction, from the surfaces which are being wiped.

To continue the longitudinal advance of the material, in a more or less helical path, the long axes of each suc- .4 cessive pair of paddles 14 may be offset, by an arcuate angle, from the long axes of the pair previously engaged by the material being treated. FIG. 11 (in which the arrows indicate the direction of rotation of the shafts) illustrates various positions of the front faces of successive paddles, the paddle designated as I being nearer to the discharge end of the machine than the other paddles; the paddle 11 being next, then the paddle III and then the paddle IV which is furthest from the discharge end, there being a angle between the long axes of successive paddles. This offsetting of the long axes of adjacent paddles also aids in the mixing action of the apparatus. As will be seen from FIG. 111, when the paddles are in the position designated as H, for example, their further movement acts to compress the material between the edges or flanks of the paddles and the walls of the housing, forcing the material into the paths of the movement of adjacent pairs of paddles.

As stated previously, the front and rear faces 52, 51 (FIGS. 8 and 9) of the paddles are advantageously fiat and, when the paddles are mounted on the shafts, are situated in planes perpendicular to said shafts; the faces of adjacent paddles are preferably close to each other; thus, the clearance between the front face of one paddle and the rear face of the next paddle may be on the order of about 0.03 inch.

It has been found advantageous to utilize, simultaneously, both the forwardly pitched paddles F14 and nonpitched paddles (hereinafter designated N14) whose front and rear profiles (N52, N51) are aligned, not offset, as illustrated in FIGS. 12 and 13. In one typical arrangement which has been employed, after a series of four full helices (on each shaft) of the feed screw elements 13, there are a sequence of six pairs of forwardly pitched paddles F14 (of the dimensions previously described) followed by one pair of otherwise identical non-pitched paddles N14, then a four-pair sequence of three pairs of forwardly pitched paddles F14 and one pair of nonpitched paddles, the latter four-pair sequence then being repeated two times more, followed by six pairs of forwardly pitched paddles. In this arrangement, the long axis 7 of the front face of each paddle is offset 45 (in the direction of rotation of the shaft) from the long axis of the front face of the next downstream paddle, as shown in FIG. 11 discussed above.

In one embodiment of this invention, there is also at least one pair of reversely pitched paddles (hereinafter designated as R14; see FIGS. 14 and 15) adjacent the discharge openings 22, 23 (FIG. 2). The reversely pitched paddles R14 are identical in construction with the forwardly pitched paddles F14, except for their mountings on the shafts. Thus, for both these types of paddles, the profiles of the rear faces are offset from the profiles of the front faces by an angle 0:. For the reversely pitched paddles R14, however, this angular offset is in a direction opposite to the direction of rotation of the shaft, while for the forwardly pitched paddles F14 the angular offset is in the same direction as the rotation of the shaft. Accordingly, the rotation of the reversely pitched paddles R14 urges the mixture in a direction toward the feed end of the housing, in exactly the same way as the rotation of the forwardly pitched paddles F14 urges the mixture away from the feed end. Corresponding portions of the paddles F14, N14 and R14 are designated by the same numerals, preceded by the appropriate letter F, N or R, respectively, in the drawing.

In one preferred embodiment, there are a series of reversely pitched paddles, in which the long axes of successive paddles of the series are offset by acute angles so as to continue the rearward motion (i.e. the motion of the mixture toward the feed end) produced by a single pair of reversely pitched paddles. FIG. 17, looking rearward from the discharge end wall 21, shows a series of three such pairs: I designates the pair closest to the end wall, H designates the next pair, and II I designates the pair furthest (in this series) from the end wall.

The presence of the reversely pitched paddles adjacent the discharge end of the apparatus changes the flow pattern of the mixture into the discharge passages and varies the relative rates of extrusion from these passages. In addition, by directing the mixture away from the end plate 21, the presence of the reversely pitched paddles helps to minimize the trapping of the mixture around the shafts 12 in the holes 37 in the end plate 21.

In one run using a series of 3 pairs of reversely pitched paddles, in the relationship illustrated in FIG. 17, mounted adjacent the two opposed discharge openings in the relationship shown in FIG. 2 and using extrusion tubes 38, 33A of the type illustrated in FIG. 20 and of 1 inch by 2 inch rectangular cross-section, the rate of extrusion from the tube 33A adjacent the opening 22 was found to be about 5 times the rate from the opposite tube 33. It was also found that the extrusion rates could be substantially equalized by adjusting the relative dimensions of the tubes, so as to establish a substantial difference in the resistance to flow through the two tubes and thereby counteract the unequal rates of extrusion. For example, by increasing the length of the tube 33A to about 6 inches (rather than the 3 inch length used in the run just described) while keeping the length of the other tube '33 at 3 inches, without changing the cross-sections of the tubes, the extrusion rates from the two tubes can be substantially equalized, without change in the densities, active contents and moisture contents of the extruded bars. Such an extension is shown in broken lines in FIG. 21. A change in the relative resistances to flow in the tubes may be established in other ways, as by the use of a screen (or other flow retarder, which may be adjustable during operation) at one tube and not in the other or by the use of screens of different mesh size in the two tubes, etc., and it is within the broader scope of this aspect of the invention to employ extrusion tubes of different flow resistances even when no rearwardly pitched paddles are present. It is also within the scope of my invention to vary the relative extrusion rates by using a smaller number of pairs of rearwardly pitched paddles (e.g. 2 pairs, such as I and 11;, of FIG. 17, or only one pair, such as I of FIG. 17), substituting pairs of forwardly pitched paddles or non-pitched paddles, or both, for the omitted rearwardly pitched paddles.

The paddle tips need not be relatively sharp. As illustrated in FIG. 16, they may be blunt and arcuate, the dimensions being adjusted so that the tips, here designated as 61, are still in closed wiping relationship with the inner walls of the housing '11 and with the edges of the mating paddles.

Another aspect of this invention relates to the use of paddles of organic polymeric plastic. When the conventional metal paddles are employed, they must be designed with a relatively large clearance between the tips 47 and the inner walls of the housing 11 and a similar clearance between these tips 47 and the flanks 48 of the mated paddles. This large designed clearance is particularly required when, as is usual, the shafts 12 on which the paddles are mounted are relatively long and slender, e.g., having a slenderness ratio above about 100; a typical shaft of this type for use in the present invention is a square shaft made of stainless steel (e.g. Type 304) which has a length of 54 inches between bearings and a cross-section which is 1% inch square. (The slenderness ratio, as is well known, is equal to l/k where l is the length and k is the radius of gyration; the slenderness ratio of the shaft having the dimensions just described is about 136.) Shafts of high slenderness ratio will tend to bend resiliently during use, so that clearances between some of the tips 47 and the surfaces they wipe decrease to well below the designed clearance. The designed clear. ance (which is the clearance between the parts when the apparatus is empty and at rest) accordingly includes a safety factor to allow for these deflections of the slender shaft in use and avoid the danger of metal-to-metal scrap ing contact and seizure between the tips and the wiped surfaces. Typically, the designed clearance is greater than 0.03 inch, e.g. 0.047 inch (which is a clearance equal to about 0.01 inch per inch of length of the paddle).

By use of paddles having tips of organic thermoplastic material, the designed clearance can be made much smaller. The greater yieldability of the plastic tips and the lower metal-to-plastic friction permit actual scraping contact with the inner surfaces of the housing, thus giving a greater shearing effect and a better heat transfer between the mixture and the jacketed walls of the housing. The designed clearance may be reduced to less than 0.03 inch e.g. 0.02 inch, 0.01 inch, 0.005 or even zero.

In a preferred form of the invention, substantially the entire paddle may be of molded plastic material; in such a construction, there may be a metallic insert for receiving the shaft 12 and for transmitting the driving force of the shaft to the plastic body of the paddle. Alternatively, only the tip portion of the paddle may be of plastic. Some or all of the paddles may be of plastic; for example, all the paddles on one shaft, or alternate pairs of paddles, may be of plastic and the other paddles of metal.

Plastics which may be employed include nylon, e.g. nylon-6 or nylon-6,6 or nylon-11; polycarbonates such as the wellknown polycarbonates of bis-phenols such as 2,2-bis-(4-hydroxyphenyl)propane (e.g. Lexan); polyacetals such as high molecular weight polyoxymethylene (end-capped as with acetate ester or methyl ether groups) or oxymethylene-oxyethylene copolymers of high (e.g. or 98%) oxymethylene content (examples of such moldable, thermoplastic acetal polymers being the products sold as Celcon and Delrin); polysulfones, such as polymers having aromatic rings and sulfo groups in the polymer chain (e.g. the polymer, having also ether groups in the chain, made by condensing p,p-dichlorodiphenylsulfone and 2,2-bis(hydroxyphenyl)propane or other bisphenol); aromatic ether polymers, such as polyphenylene oxide. Thermoset polymers, such as epoxy resins or phenolic resins, may also be used. The polymeric plastic employed should of course be one which is resistant to the environment (e.g. elevated temperature and/or acidic conditions) in which it is to be used.

Preferably, the plastic paddles make a slide fit with the inner surfaces of the housing. Thus, one may mold the plastic paddles to such size that their tips make contact with said housing surfaces when the paddles are installed on the shafts. One pair of paddles may be in stalled in the apparatus and the apparatus may then be operated until the tips of the plastic pair have become worn off (or deformed) sufficiently by contact with the inner surface of the housing, so as to make a slide fit (e.g. 0.005" clearance) with said surface. Then another mated pair of paddles may be similarly installed and run in, and so forth, until all the desired plastic paddles are fitted to the apparatus.

As indicated previously, the apparatus may be employed for the manufacture of detergent laundry bars, comprising a water-soluble anionic organic synthetic detergent and an inorganic builder salt, the amount of the builder salt being greater than the amount of detergent. Descriptions of suitable detergents, builder salts, and other ingredients their proportions and the conditions of operation are found for example,'in my application Scr. No. 509,803, previously mentioned. For example, the detergent may be supplied as a preformed salt (e.g. a sodium alkylbenzenesulfonate) premixed with finely divided builder salts, and the mixture may be blended with a predetermined quantity of water in the apparatus. Alternatively, the detergent may be supplied in its acid form (e.g. as alkylbenzenesulfonic acid) and neutralized, in the apparatus, in admixture with the builder salt; in this case, the dry finely divided builder salts may be fed into the hopper 16, the stream of detergent acid may be fed into the port 17 (FIG. 1), and a stream of aqueous neutralizing agent (e.g. NaOH) may be fed into a second port 64, or the neutralizing agent may be supplied in dry condition (e.g. as Na CO present in the builder salt mitxure) and a stream of water may be fed to the second port 64. When the apparatus is used for making an aerated bar, air or other gas under pressure may be injected through suitable ports, e.g. through third and fourth ports 66 and 67.

When the apparatus is used for the manufacture of the aerated bar, particularly when the in situ neutralization technique is employed, blowback of the injected gas can be prevented, according to another feature of this invention, by feeding the solid finely divided ingredients into the hopper under positive pressure. For this purpose, there is provided a screw feeder 71 (FIG. 18) having therein a driven continuously rotating worm 72 of substantial length as compared with its diameter (e.g. 30 inches long and 5 inches in diameter). The screw feeder 71 is preferably of the type which compacts the powdered material fed thereto so that when the powdered material is supplied thereto as the proper rate, it forms in effect a slug of densely packed material which is discharged continuously from the screw feeder outlet 73 and into the hopper 16. An airtight cover 74 prevents leakage of gas from the hopper. The screw feeder may be mounted with its axis at an angle to the horizontal axes of the shafts 12, e.g. with its axis substantially vertical as illustrated in FIG. 18, with a space for free fall, through the hopper, of the pieces leaving the screw feeder. Alternatively, the driven screw feeder 71 may be mounted horizontally (FIG. 23) and there may be an enclosed free-fall space of several feet (e.g. through a substantially airtight chute 76) between its outlet and the sealed hopper 16. It is preferred to supply the builder salt mixture, in more or less powdery or fine granular condition, to the inlet of the screw feeder 71 by means of a conventional continuous vibratory feeding device, such as the vibrated feed screw 77.

For preventing blowback of injected gas, according to another feature of this invention, the feed screw elements mounted on the shafts 12 are themselves modified to provide a zone in which the edges of the flights of said elements are broad whereby to cause the materials being fed to form a sealing layer between said broad edges and the interior wall surface of the housing. In the embodiment shown in FIG. 22, each of the two feed screws, here designataed as 113, has a continuous helical flight intermeshing with the continuous flight of the other feed screw; there is a sharp edge 116 on that portion 117 of the flight which is under the hopper 16 while there is a broad flat edge 118 on that portion 119 of the flight which is completely surrounded by the housing 11 (i.e. which is in the main barrel of the apparatus).

As shown in FIG. 22, the flight 114 in both the portions 117 and 119 is preferably concave and arcuate in cross-section. Typically, for a feed screw having an outer diameter of about 5 inches, the sharp-edged portion 117 may have an edge 116 about A inch or less in width, while the portion 119 may have an edge 118 more than A; inch, e.g. A inch, in Width.

The presence of the sharp-edged portion gives excellent performance in breaking up, chopping and pulverizing lumps in the solid feed and in forcing the material from the hopper into the main barrel, and minimizes or avoids the tendency of the feed material to form bridges across the flight and the hopper. In one embodiment, the outer diameter of each feed screw 113 is about 5 inches; its pitch (i.e. the distancce between successive turns of the flight) is about 2 inches; the radial distance between the crest of the flight and its root portion is about 1% inches; the hopper opening measures about 4 inches in the axial direction; and the sharp-edged portion 117 extends over about 4 inches of the shaft, there being about 2 turns of the broad-edged flight portion completely within the housing.

The tips of the feed screw flights, or the entire flights, may be of polymeric plastic material, and may be of the same material as the plastic tips of the paddles previously described, using the same clearances. The inner walls of the housing around the broad edged portions of the flights may be faced with, or made entirely of, similar plastic or may be faced with natural or synthetic vulcanized rubber.

In another embodiment of the invention, particularly suitable for use with mixing apparatus of large diameter and correspondingly large capacity, there are a plurality of extrusion tubes opening onto one side (or onto each side) of the mixing apparatus at its discharge end. Thus, as illustrated in FIG. 24, a plate 121, adapted to cover the discharge opening 23, may have four parallel rectangular extrusion tubes 122 (the cross-section of each tube being, for example 1 inch x 2 inches) for the extrusion of a corresponding number of continuous rectangular bars; a similar manifold arrangement may be located at the opposite opening 22, or the latter may be closed off, or may be fitted with a lesser number of extrusion tubes.

The extrusion openings (e.g. the outlets of the extrusion tubes) typically have a cross-sectional area of at least about 2 square inches, one dimension (at least equivalent to the thickness of the individual laundry bars) being in the range of about A to 3 inches and the other dimension (at least equivalent to the width of the individual laundry bar) being at least about 2 inches. Extrusion openings of larger cross-sectional area may be used to produce larger extrudates, whose dimensions are multiples of the thickness or width of the individual bars, in which case the extrudate may then be cut lengthwise, as well as transversely, in the process of forming the individual bars.

It is to be understood that the foregoing detailed description is given merely by way of illustration, and that variations may be made therein without departing from the spirit of the invention.

What is claimed is:

1. In an apparatus for the continuous mixing of materials and for the continuous discharge of the resulting mixture, said apparatus comprising a housing having a feed end and a discharge end, a pair of parallel shafts in said housing, means for driving said shafts to rotate both shafts in the same direction, said shafts having thereon a series of pairs of mated mixing and shearing paddles arranged lengthwise of said shafts and within said housing, each of said mated pairs comprising a paddle mounted on one of said shafts and a cooperating and aligned paddle mounted on the other of said shafts, each mated paddle being elongated and having an arcuate edge and a wiping tip, the construction and arrangement being such that during the rotation of said shafts and of the paddles carried thereby, said tips wipe against the arcuate edges of the mated, paired paddles, said pairs of paddles including forwardly pitched pairs whose edges and tips are pitched in a direction to move the materials in said housing away from said feed end and toward the discharge end, the improvement which comprises a discharge opening in said housing adjacent said discharge end for the discharge of said mixture in a direction generally transverse of said shafts, said discharge opening having an edge more remote from said feed end and an upstream edge close to said feed end, and, mounted on said shafts and adjacent said more remote edge, a mated pair of said mixing and shearing paddles, the paddles of said latter pair being reversed pitch paddles having their mating edges and tips pitched in a direction to move the mixture toward said feed end.

2. Apparatus as in claim 1 in which the inner walls of the housing conform substantially to the shape of intersecting circular cylinders centered on the axes of said shafts and of sufficient radius to accommodate the rotation of said paddles, the construction and arrangement being such that, during the rotation of said shafts and of said mated paddle pairs, a tip of each mated paddle wipes successively against the arcuate edge of its mate and the inner wall of the housing.

3. Apparaus as in claim 2 in which the two mated paddles of each pair are of substantially the same size and shape, each mated paddle having two diametrically opposed tips joined by two convex arcs of intersecting equiradial circles, the long axis joining the tips of each paired paddle being at right angles to the corresponding long axis of the other paddle of each pair, each paddle having a front face and a rear face, both said faces being in planes transverse to said central plane, the front face and rear face of some of said paddles being aligned in a direction parallel to the shafts, the front face and rear face of said forwardly pitched paddles being offset, in one direction, by an acute angle about the respective shafts on which the paddles are mounted, and the front face and rear face of said rearwardly pitched paddles being likewise offset, but in the opposite direction.

4. Apparatus as in claim 3 in which said shafts lie in a substantially horizontal common plane, said housing has a pair of said discharge openings adjacent to said reversely pitched paddles, the paired discharge openings being oppositely directed, said housing also having an end wall, adjacent said reversed pitched paddles, said end wall having holes for receiving said shafts.

5. Apparatus as in claim 4 in which the paired openings open, respectively, onto elongated, substantially fully enclosed passages for the extrusion of a pair of continuous bars of said mixture through said passages.

6. Apparatus as in claim 5 in which upstream of said 'discharge opening there are paddle pairs staggered on said shafts in a direction to impart a downstream movement to said mixture and in which downstream of said upstream edge there are paddle pairs staggered on said shafts in a direction to impart an upstream movement to said mixture.

7. Apparatus as in claim 1 in which said housing has an end wall, adjacent said reversed pitch paddles, said end wall having holes for receiving said shafts.

8. Apparatus as in claim 1 in which said shafts are substantially horizontal.

9. Apparatus as in claim 1 in which said housing has a pair of said discharge openings adjacent to said reversely pitched paddles, the paired discharge openings being oppositely directed.

10. Apparatus as in claim 1 in which said discharge opening opens onto an elongated, substantially fully en; closed passage for the extrusion of a continuous bar of said mixture therethrough.

11. Apparatus as in claim 1 in which upstream of said discharge opening there are paddle pairs staggered on said shafts in a direction to impart a downstream movement to said mixture, and in which downstream of said upstream edge there are paddle pairs staggered on said shafts in a direction to impart an upstream movement to said mixture.

12. In an apparatus for the continuous mixing of materials, said apparatus having a housing, a pair of parallel shafts in said housing, means for driving said shafts to rotate both shafts in the same direction, said shafts having thereon a series of pairs of mated mixing and shearing paddles arranged lengthwise of said shafts and within said housing, each of said mated pairs comprising a paddle mounted on one of said shafts and a cooperating and aligned paddle mounted;on the other of said shafts, each mated paddle being elongated and having an arcuate edge and a wiping tip, the inner wall of the housing conforming substantially to the shape of intersecting circular cylinders centered on the axes of said shafts and of sufficient radius to accommodate the rotation of said paddles, the construction and arrangement being such that, during the rotation of said shafts and of said mated paddle pairs a tip of each mated paddle wipes successively against the arcuate edge of its mate and the inner wall of the housing, the improvement in which said tips are of polymeric plastic material.

13. Apparatus as in claim 12 and including paddles whose plastic tips pass within 0.02 inch of the inner wall which they wipe.

14. Apparatus as in claim 12 and including paddles whose plastic tips make actual physical contact with the inner wall which they wipe.

15. Apparatus as in claim 12 in which the slenderness ratio of the shafts is greater than about :1.

16. In an apparatus for the continuous mixing of materials and for the continuous discharge of the resulting mixture, said apparatus comprising a housing having a feed end and a discharge end, a pair of parallel shafts in said housing, means for driving said shafts to rotate both shafts in the same direction, said shafts having thereon a series of pairs of mated mixing and shearing paddles arranged lengthwise of said shafts and within said housing, each of said mated pairs comprising a paddle mounted on one of said shafts and a cooperating and aligned paddle mounted on the other of said shafts, each mated paddle being elongated and having an arcuate edge and a wiping tip, the construction and arrangement being such that during the rotation of said shafts and of the paddles carried thereby, said tips wipe against the arcuate edges of the mated, paired paddles, said apparatus being constructed and arranged to move the materials in said housing away from said feed end and toward the discharge end on rotation of said shafts, and having means for introducing a gas under superatmospheric pressure into the mixture in said housing and an inlet at said feed end for the introduction of solids into said housing, the improvement which comprises a screw conveyor having a substantially gas tight seal to said inlet for introducing said solids in tighly packed condition resistant to the flow of gas therethrough whereby to reduce blowback of said gas under superatmospheric pressure toward said feed end.

17. Apparatus as in claim 16 in which said shafts have intermeshing feed screw elements arranged to receive the solid introduced by said conveyor at said inlet and to forward said solids toward the discharge end on rotation of said shafts.

18. In an apparatus for the continuous mixing of materials and for the continuous discharge of the resulting mixture, said apparatus comprising a housing having a feed end and a discharge end, a pair of parallel shafts in said housing, means for driving said shafts to rotate both shafts in the same direction, said shafts having thereon a series of pairs of mated mixing and shearing paddles arranged lengthwise of said shafts and within said housing, each of said mated pairs comprising a paddle mounted on one of said shafts and a cooperating and aligned paddle mounted on the other of said shafts, each mated paddle 'being elongated and having an arcuate edge and a wiping tip, the construction and arrangement being such that during the rotation of said shafts and of the paddles carried thereby said tips wipe against the arcuate edges of the mated, paired paddles, said apparatus being constructed and arranged to move the materials in said housing away from said feed end and toward the discharge end on rotation of said shafts, and having means for introducing a gas under superatmospheric pressure into the mixture in said housing and an inlet at said feed end for the introduction of solids into said housing, and having intermeshing feed screw flights on said shafts at said feed end, said flights having edges moving across, and close to, the inner walls of the hous ing, the improvement in which the flight edges are sharp at said inlet and are broad downstream of said inlet whereby to cause the materials being fed to said appartus to form a sealing layer between said broad edges and the interior wall surface of the housing.

19. In an apparatus for the continuous mixing of material and for the continuous discharge of the resulting mixture, said apparatus comprising a housing having a feed end and a discharge end, a pair of parallel shafts in said housing, means for driving said shafts to rotate both shafts in the same direction, said shafts having thereon a series of pairs of mated mixing and shearing paddles arranged lengthwise of said shafts and within said housing, each of said mated pairs comprising a paddle mounted on one of said shafts and a cooperating and aligned paddle mounted on the other of said shafts, each mated paddle being elongated and having an arcuate edge and a wiping tip, the construction and arrangement being such that during the rotation of said shafts and of the paddles carried thereby, said tips wipe against the arcuate edges of the mated, paired paddles, said pairs of paddles including forwardly pitched pairs whose edges and tips are pitched in a direction to move the materials in said housing away from said feed end and toward the discharge end, the improvement which comprises a pair of opposed discharge passageways comprising extrusion tubes at said discharge end, for the discharge of said mixture in a direction generally transverse of said shafts, the flow resistances in said discharge passageways being substantially different.

References Cited UNITED STATES PATENTS 2,631,016 3/1953 Laubarede 259-6 2,814,472 11/1957 Erdmenger 259-104 3,195,868 7/1965 Loomans 259-104 3,198,491 8/1965 Loomans 259-6 ROBERT W. JENKINS, Primary Examiner. 

1. IN AN APPARATUS FOR THE CONTINUOUS MIXING OF MATERIALS AND FOR THE CONTINUOUS DISCHARGE OF THE RESULTING MIXTURE, SAID APPARATUS COMPRISING A HOUSING HAVING A FEED END AND A DISCHARGE END, A PAIR OF PARALLEL SHAFTS IN SAID HOUSING, MEANS FOR DRIVING SAID SHAFTS TO ROTATE BOTH SHAFTS IN THE SAME DIRECTION, SAID SHAFTS HAVING THEREON A SERIES OF PAIRS OF MATED MIXING AND SHEARING PADDLES ARRANGED LENGTHWISE OF SAID SHAFTS AND WITHIN SAID HOUSING, EACH OF SAID MATED PAIRS COMPRISING A PADDLE MOUNTED ON ONE OF SAID SHAFTS AND A COOPERATING AND ALIGNED PADDLE MOUNTED ON THE OTHER OF SAID SHAFTS, EACH MATED PADDLE BEING ELONGATED AND HAVING AN ARCUATE EDGE AND A WIPING TIP, THE CONSTRUCTION AND ARRANGEMENT BEING SUCH THAT DURING THE ROTATION OF SAID SHAFTS AND OF THE PADDLES CARRIED THEREBY, SAID TIPS WIPE AGAINST THE ARCUATE EDGES OF THE MATED, PAIRED PADDLES, SAID PAIRS OF PADDLES INCLUDING FORWARDLY PITCHED PAIRS WHOSE EDGES AND TIPS ARE PITCHED IN A DIRECTION TO MOVE THE MATERIALS IN SAID HOUSING AWAY FROM SAID FEED END AND TOWARD THE DISCHARGE END, THE IMPROVEMENT WHICH COMPRISES A DISCHARGE OPENING IN SAID HOUSING ADJACENT SAID DISCHARGE END FOR THE DISCHARGE OF SAID MIXTURE IN A DIRECTION GENERALLY TRANSVERSE OF SAID SHAFTS, SAID DISCHARGE OPENING HAVING AN EDGE MORE REMOTE FROM SAID FEED END AND AN UPSTREAM EDGE CLOSE TO SAID FEED END, AND MOUNTED ON SAID SHAFTS AND ADJACENT SAID MORE REMOTE EDGE, A MATED PAIR OF SAID MIXING AND SHEARING PADDLES, THE PADDLES OF SAID LATTER PAIR BEING REVERSED PITCH PADDLES HAVING THEIR MATING EDGES AND TIPS PITCHED IN A DIRECTION TO MOVE THE MIXTURE TOWARD SAID FEED END. 